Binary Search Tree implementation in Python

gistfile1.py

'''
   by Adrian Statescu <[email protected]>
   Twitter: @thinkphp
   G+     : http://gplus.to/thinkphp
   MIT Style License
'''
'''
   Binary Search Tree
   ------------------

   Trees can come in many different shapes, and they can vary in the number of children allowed per node or in the way
   they organize data values within the nodes. One of the most commonly used trees in computer science is the binary tree.
   A binary tree is a tree in which each node can have at most two children. On child is identified as the left child and
   the other as the right child. The topmost node of the tree is known as the root node.It provides the single acccess point
   into the structure. The root node is the only node in the tree that does not have an incoming edge (an edge directed towart it)
   By definition every non=empty tree must have contain a root node.
  
'''

class Node:

      def __init__(self,info): #constructor of class

          self.info = info  #information for node
          self.left = None  #left leef
          self.right = None #right leef
          self.level = None #level none defined

      def __str__(self):

          return str(self.info) #return as string


class searchtree:

      def __init__(self): #constructor of class

          self.root = None


      def create(self,val):  #create binary search tree nodes

          if self.root == None:

             self.root = Node(val)

          else:

             current = self.root

             while 1:

                 if val < current.info:

                   if current.left:
                      current = current.left
                   else:
                      current.left = Node(val)
                      break;      

                 elif val > current.info:
                 
                    if current.right:
                       current = current.right
                    else:
                       current.right = Node(val)
                       break;      

                 else:
                    break 

      def bft(self): #Breadth-First Traversal

          self.root.level = 0 
          queue = [self.root]
          out = []
          current_level = self.root.level

          while len(queue) > 0:
                 
             current_node = queue.pop(0)
 
             if current_node.level > current_level:
                current_level += 1
                out.append("\n")

             out.append(str(current_node.info) + " ")

             if current_node.left:

                current_node.left.level = current_level + 1
                queue.append(current_node.left)
                  

             if current_node.right:

                current_node.right.level = current_level + 1
                queue.append(current_node.right)
                      
                 
          print "".join(out)   


      def inorder(self,node):
            
           if node is not None:
              
              self.inorder(node.left)
              print node.info
              self.inorder(node.right)


      def preorder(self,node):
            
           if node is not None:
              
              print node.info
              self.preorder(node.left)
              self.preorder(node.right)


      def postorder(self,node):
            
           if node is not None:
              
              self.postorder(node.left)
              self.postorder(node.right)
              print node.info

                        
tree = searchtree()     
arr = [8,3,1,6,4,7,10,14,13]
for i in arr:
    tree.create(i)
print 'Breadth-First Traversal'
tree.bft()
print 'Inorder Traversal'
tree.inorder(tree.root) 
print 'Preorder Traversal'
tree.preorder(tree.root) 
print 'Postorder Traversal'
tree.postorder(tree.root)